Am> PHYSIOLO&T OF THE SPOHGIAD^. 
1095 
Leucogtpsia, Bowerbank. 
Sponge massive, without cloacae ; formed of irregularly disposed membranous tissues and 
spicula. Oscula at the external surface. 
The sponges of this genus are still further removed in structural character from the 
more highly organized genera of calcareous sponges Grantia and Leucosolenia than the 
genus Leuconia is. In the arrangement of the interstitial membranes, and the mode of 
dispersion on them of the skeleton-spicula, there is a manifest similitude to the structural 
peculiarities of the genus Eymeniacidon among the Silicea, and we find a corresponding 
simplicity in the characters of the spicula, in Leucogypsia the type of this genus. There 
are no regularly determined cloacae projected from the surface as in Leuconia; and the 
excurrent canals of the sponge merge into each other, until they unite in one large canal 
immediately beneath the osculum, in the manner generally prevailing in the great 
mass of Halichondroid sponges. These large canals have defensive spicula similar in 
structure to those of the other genera of calcareous sponges. The only known 
British species of this genus is L. Oossei, Bowerbank, MS. ; but I am acquainted with 
an exotic species, L. algoaensis, Bowerbank, MS., which is not uncommon on specimens 
of Zoophytes and Fuci from Algoa Bay and its neighbourhood. Plate LXXII. fig. 4. 
Synopsis of the Suborders of the Silicea and Keratosa, 
Order II. SILICEA. 
Suborder I. Spiculo-radiate skeletons. Not 
fasciculi or separately from the base or 
1. Geodia, Lamarck. 
2. Pachymatisma, Bowerbank. 
3. Ecionemia, Bowerbank. 
4. Alcyoncellum, Quoy et Gaimard. 
5. Polymastia, Bowerbank. 
6. Halyphysema, Bowerbank. 
7. Ciocalypta, Bowerbank. 
.’eticulate. Composed of spicula radiating in 
axis of the sponge. 
8. Tethea, Lamarck. 
9. Halicnemia, Bowerbank. 
10. Dictyocylindrus, Bowerbank. 
11. Phakellia, Bowerbank. 
12. Microciona, Bowerbank. 
13. Hymeraphia, Bowerbank. 
14. Hymedesmia, Bowerbank, 
Suborder II. Spiculo-membranous skeletons. Composed of membranous structure, having 
spicula irregularly dispersed on their surfaces. 
Eymeniacidon, Bowerbank. 
Suborder III. Spiculo-reticulate skeletons. Skeletons continuously reticulate in struc- 
ture, but not fibrous. 
1. Ealichondria, Fleming. 
2. Eyalonema, Gray. 
3. Isodictya, Bowerbank. 
4. Spongilla, Linnaeus. 
7 K 
MDCCCLXII. 
